All speakers, including car speakers and those earbuds, need to be broken-in, in order to loosen up the diaphragm and to take the speakers to their full potential. There are also many rigorous methods of breaking-in, from using white and pink noise to playing different types of music. The point is to excite the speakers using all available frequencies.

Some speakers take more than other to break-in. Those $20 desktop speakers will probably make nil difference when broken in whereas other hi-fi speakers can take upwards of 200 hours to properly break-in and there is significant audible and detectable difference after break-in.

For our HK and BMW car speakers, just play the music you want and they'll start to sound better (i.e. crisp, deep, etc)